A well system (e.g., an oil or gas well for extracting fluids or gas from a subterranean formation) can include various electronic devices in a wellbore. For example, the well system can include a pressure sensor for detecting the pressure in the wellbore. Such sensors may be part of an intelligent completion. The well system may include advanced sensor systems such as electromagnetic (EM) reservoir monitoring systems that consist of multiple electronic devices. In many cases, the electronic devices can be positioned far from the well surface. For example, some electronic devices can be positioned more than 20,000 feet from the well surface. Controlling electronic devices at such far distances using traditional power line systems can present challenges. For example, high-frequency electrical signals, such as those transmitted over copper cables in power line systems, can significantly attenuate over large distances. These electrical signals can further degrade in the presence of the high temperatures commonly found in wellbores.